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Focusing 90mm AA at f2 and 3 meters impossible with Rangefinder -at least for me


dem331

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There are so many factors involved when you try to find out whether you get exact focus with a demanding lens like the 90mm Summicron Apo-Asph.

 

  • Eyesight: I recently  learned that I need different varifocals for different distances. Not just different glasses, but different varifocals: one is  o.k. from short distance to infinity, but another one is much better up to 2 or 3m, whilst it is almost unusable for infinity. So I'll have different experience with both varifocals trying the lens. When I wear  non-varifocal glasses the results will be much different again. Contrast and lighting may also make much difference for different conditions of your eyesight.
  • Focus shift: the lens we are talking about has some focus shift. Older examples from the pre-digital times usually where calibrated at f:4 or f:5.6, so the are slightly off at f:2. Zeiss says that officially, Leica doesn't tell but they change the calbration to f:2, when you send it in. Afterwards it will be slightly off at f:4, though larger dof will compensate better.
  • Stability: Without a tripod results will be much more hit and miss than using one, even with a tripod you might have differences if your shutter time is too long. The method without a tripod rocking forward or back, which is good for say 50mm at f:2,8, will almost guarantee you many misses with 90mm f:2.

One may find many more factors causing suboptimal results. There is no real chance to get the optimum if you don't restrict your fotography to laboratory conditions. So the "old" way of using smaller openings with more dof may be the most practical one.

Edited by UliWer
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  • [...] Focus shift: the lens we are talking about has some focus shift. Older examples from the pre-digital times usually where calibrated at f:4 or f:5.6, so the are slightly off at f:2. [..]

 

Neither my 90/2 v3 nor my 90/2 apo show the least focus shift i must say. Both have been calibrated for digital though.

Edited by lct
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True friend, when someone tells me he wants telemetric ask him what his visual acuity, one thing to have the corrected view because you wear glasses or contact lenses and other visual acuity is the total you have.

 

This is important.

 

It's easy to focus at 1 meter with f2, or f0,95, I do it every day and do well in motion.

 

 

Jhon you are right about visual acuity, and it not being equivalent to corrected eyesight.  I have special problems in low light.  I also have a little bit of astigmatism which is difficult to correct with contact lenses, so I have an additional disadvantage.

 

All the same, when you are talking about perfect focus, I think it is hit and miss on a moving subject at f2 and 1-3 meters (and more miss than hit).  By perfect focus I mean an image that is indistinguishable from one taken using the EVF and  magnified to the largest possible factor in playback mode to check focus.

 

Having said that, and image that does not have perfect focus may be perfectly fine for the use intended.

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Could be your lens. To be honest the 75APO is far easier to hit critical focus then the 90APO. 

But I don't have a problem using the 90APO, just takes a lot of practice and good eye sight. The 1.4x won't help you. You're much better off buying a diopter (even if you don't need one). Seems to help my friend who doesn't need/wear glasses and has tried both magnifiers. 

 

I also understand what you mean about moving the lens ring ever so slightly but not quite seeing the change in the RF patch. It is "somewhat" a limitation of the RF design, but again I don't have issues focusing a Noctilux which is the same principle. I think at some point you have to give up on the idea of seeing and you have to just "feel" that last little bit. I know it sounds stupid but somehow it works.

 

Worst case scenario, get a Leica SL :D

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  • 4 weeks later...

I am pretty new to Leica, but using EVF-2 managed to find good ways to focus Summicron 90mm APO (on  MM Typ 246)

Anyway, the sample image is attached. Make your conclusion, may be I am just wrong... Distance to the subject somewhat between 2-3 meters...

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Here is another shot with EVF-2, MM Typ 246, 90 mm Summicron APO

 

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Could be your lens. To be honest the 75APO is far easier to hit critical focus then the 90APO. 

But I don't have a problem using the 90APO, just takes a lot of practice and good eye sight. The 1.4x won't help you. You're much better off buying a diopter (even if you don't need one). Seems to help my friend who doesn't need/wear glasses and has tried both magnifiers. 

 

I also understand what you mean about moving the lens ring ever so slightly but not quite seeing the change in the RF patch. It is "somewhat" a limitation of the RF design, but again I don't have issues focusing a Noctilux which is the same principle. I think at some point you have to give up on the idea of seeing and you have to just "feel" that last little bit. I know it sounds stupid but somehow it works.

 

Worst case scenario, get a Leica SL :D

Moving the focus ring from infinity - always- and avoiding "hunting" by not going back and forth around the focus point is the best way to get consistent focus. Although the tolerances in the whole chain of the focusing mechanism are as minimal as they can be, they still add up and moving the focusing ring from close  does introduce an error.

 

Yes, the EVF is exact, but not a particularly nice experience with its own drawbacks. I would advise putting some effort into using the rangefinder whenever possible - much more satisfying.

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Hello Enrique,

 

Here are some suggestions you might want to consider:

First: Put your camera on a tripod & check to see that the focus in the viewfinder matches the focus in the range/viewfinder.

 

Do this @ F2, F4, F8 & F11.

 

Do each of those @ 1 meter, 3 meters, 10 meters & Infinity (ie: The Moon).

 

Then remember that a magnification in image size means that there is a matching magnification of image shake since sometimes what people perceive as an out of focus image is instead: A lack of sharpness that is due to camera/lens movement magnified by increased image magnification.

 

After checking all of this you might also consider rotating your range/viewfinder window 45 degrees counter clockwise or clockwise while focusing. This way lines come together from 2 directions at the same time instead of simply horizontally or vertically. This is something that has been done by rangefinder photographers at least since the 1930's.

 

Next you might try a small, sturdy table tripod with a large ball head & a cable release*.

 

This can be put against a rock or a tree, against a wall or on the inside frame or on the inside top of a door frame. On a car with the engine turned off, or even on a table. Against my chest such a device gives me +2 stops of added stability in terms of hand held shutter speeds. 

The more you use this spiffy combination the more times & places you find to use it. When you are not using it it closes up & takes about the same space as a lens.

 

Best Regards,

 

Michael

 

* Cable releases are more useful than some people might think. Either in combination with a large ball head & a tripod or with the camera alone.

Edited by Michael Geschlecht
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